This invention relates to making a connection of pipes with each other, or in the case of making a connection of a pipe with another connecting section as a joint or the like, to making a connection thereof by the employment of a special connector. Conventional methods of making connections by welding are known, for example in Patent No. 1,199,072 of West Germany. In this example, a compression ring is set in place on around the outer circumferential wall of a cylinder at the connecting end of a pipe to cover the same and a cap is put on the compression ring for subjecting the same to collapsed deformation, to thus provide such a scarfed area wherein the compression ring and the cap nut are combined with each other in such a manner that proper compressive force is applied in the contact section thereof. The compression ring is subjected to collapsed deformation by way of the scarfed area, furthermore, the connecting end of the internal pipe is likewise subjected to collapsed deformation, while revolving the said cap nut, thus forming the compression ring and the connecting end of the pipe into an integral entity in terms of mechanical constitution. Such a means wherein the internal peripheral surface of the compression ring has a series of convex threads having a sharp-angled edge properly formed thereon, and the convex threads are engaged with the cylindrical external peripheral wall of the pipe at the connecting end thereof, for the purpose of improving watertightness. This technical idea is rather limited in the applicability thereof to such a thick metal pipe as is free from having the shape and the rigidity thereof deteriorated even in the case of being subjected to collapsed deformation, due to the principal construction thereof wherein collapsed deformation is caused to take shape at the connecting end of the pipe.
As the demand for such pipes have increasing emphasis placed on the preservation in heat of a substance to be transferred by means of a pipeline, wherefrom such composite pipes are given a coat of a diabatic layer of hardened expanded vinyl chloride or the like are being manufactured in a large quantity; however, now that the pipes of this category actually in use are thin metal pipes, the above-mentioned connector designed with collapsed deformation taken as the basic idea therefor cannot be expected to be sufficient in terms of mechanical connecting force, and the connection by means of such a connector is prone to be subjected either to disconnection or to deformation in the shape thereof due to bending force and, hence is unstabilzed. To put it otherwise, it is anything but desirable in engineering terms to subject a thin metal pipe to collapsed deformation.
With such a situation duly taken in consideration, such a construction of a connector or a connecting section as is well capable of displaying thorough and necessary connecting force and has sufficient stability against external bending force ought to be developed for the use of thin metal pipes as well where to the conventional technology proves rather hard to be properly applied.
The purpose of the present invention lies in providing such a novel construction of a connector as makes use of diameter-extending plastic deformation capable of forming the internal wall of cylinder into a partially ring-shaped surface of the connecting end of a pipe, in leiu of making use of the conventional collapsed deformation.
Another purpose of the present invention lies in adding to this connector such a construction for fitting a packing member as displays superb airtightness well capable of manifesting the effect thereof to a gaseous matter, as well as to a liquid matter.
Besides, the present invention has such a merit that, when employed for a composite pipe made of a thin metal material and covered with a coat of hardened expanded vinyl chloride or the like on the external peripheral wall over the entire length thereof, and has a feature in that the applicable scope of the connector is properly extended in such a manner as to be generally employed for any thin pipe.